Method of processing control information in a mobile communication system

ABSTRACT

A method of processing control information in a mobile communication system is disclosed, by which an RRC connection setup can be quickly completed and by which control information can be processed without an unnecessary standby of a mobile terminal. The present invention includes the steps of receiving a plurality of protocol data units transmitted plural time from a transmitting side via one common logical channel by an RLC (radio link control) entity operating in a UM (unacknowledged mode) and having a receiving window and a timer, re-ordering a plurality of the received protocol data units using sequence numbers of a plurality of the received protocol data units, the receiving window and the timer, reassembling at least one service data unit by processing a plurality of the re-ordered protocol data units, and delivering the at least one service data unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No.11/461,382 filed Jul. 31, 2006, pending, the contents of which arehereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control information processingmethod, and more particularly, to a method of processing controlinformation in a mobile communication system. Although the presentinvention is suitable for a wide scope of applications, it isparticularly suitable for preventing a user equipment from standing byunnecessarily.

2. Discussion of the Related Art

FIG. 1 is a block diagram of a network structure of UMTS (universalmobile telecommunications system).

Referring to FIG. 1, a universal mobile telecommunications system(hereinafter abbreviated UMTS) mainly includes a user equipment(hereinafter abbreviated UE), a UMTS terrestrial radio access network(hereinafter abbreviated UTRAN) and a core network (hereinafterabbreviated CN).

The UTRAN includes at least one radio network sub-system (hereinafterabbreviated RNS). And, the RNS includes one radio network controller(hereinafter abbreviated RNC) and at least one base station (hereinaftercalled Node B) managed by the RNC. And, at least one or more cells existin one Node B.

FIG. 2 is a diagram of architecture of a radio protocol used for UMTS.

Referring to FIG. 2, radio protocol layers exist as pairs in both UE andUTRAN to take charge of data transmission in a radio section.

The respective radio protocol layers are explained as follows.

First of all, a physical layer PHY, which is a first layer, plays a rolein transferring data to a radio section using various radio transfertechniques. The physical layer PHY is connected to a layer MAC as anupper layer via transport channels. And, the transport channels aremainly classified into dedicated transport channels and common transportchannels according to whether the corresponding channel is shared ornot.

A second layer includes MAC, RLC, PDCP and BMC layers.

First of all, a MAC layer plays a role in mapping various logicalchannels to various transport channels, respectively and also performs afunction of logical channel multiplexing that plays a role in mappingvarious logical channels to one transport channel. The MAC layer isconnected to an RLC layer of an upper layer via a logical channel. And,the logical channel is mainly classified into a control channel fortransferring information of a control plane and a traffic channel fortransferring information of a user plane according to a type ofinformation that is transferred.

A radio link control (hereinafter abbreviated RLC) layer is responsiblefor guaranteeing a quality of service (hereinafter abbreviated QoS) ofeach radio bearer and also takes charge of a transfer of correspondingdata. The RLC leaves one independent RLC entity at each RB to guaranteean intrinsic QoS of RB. The RLC offers three kinds of RLC modesincluding a transparent mode (hereinafter abbreviated TM), anunacknowledged mode (hereinafter abbreviated UM) and an acknowledgedmode (hereinafter abbreviated AM) to support various QoS. And, the RLCplays a role in adjusting a data size to enable a lower layer totransfer data to a radio section. For this, the RLC plays a role insegmenting and concatenating data received from an upper layer.

A PDCP layer is placed above the RLC layer and plays a role intransferring data, which is transferred using an IP packet such as anIPv4 and an IPv6, efficiently in a radio section having a relativelysmall bandwidth. For this, the PDCP layer performs a header compressionfunction, by which information mandatory for a header of data istransferred to raise transport efficiency in a radio section. Sinceheader compression is a basic function of the PDCP layer, the PDCP layerexists in a packet service domain (hereinafter abbreviated PS domain)only. And, one PDCP entity exists for each RB to provide an effectiveheader compression function to each PS service.

In the second layer, a BMC (broadcast/multicast control) layer isprovided above the RLC layer. The BMC layer schedules a cell broadcastmessage and performs broadcasting to UEs located in a specific cell.

A radio resource control (hereinafter abbreviated RRC) layer located ina lowest part of a third layer is defined in a control plane only. TheRRC layer controls parameters of the first and second layers to beassociated with establishment, re-configuration and release of RBs andtakes charge of controlling logical, transport and physical channels. Inthis case, the RB means a logical path provided by the first and secondlayers of a radio protocol for data transfer between UE and UTRAN. And,RB establishment means a process of regulating characteristics of radioprotocol layers and channels to offer a specific service andestablishing specific parameters and operational methods. When an RRClayer of a specific UE and to an RRC layer of UTRAN are connectedtogether to exchange RRC messages with each other, the corresponding UElies in an RRC connected state. IF they are not connected together, thecorresponding UE lies in an idle state.

The RLC layer is further explained in detail as follows.

First of all, basic functions of the RLC layer are a QoS guarantee ofeach RB and a corresponding data transfer. Since an RB service is aservice that the second layer provides to an upper layer, the entiresecond layer has influence on QoS. And, the RLC has the greatestinfluence. The RLC leaves an independent RLC entity at each RB toguarantee the intrinsic QoS of RB and offers three kinds of RLC modes ofTM, UM and AM. Since the three RLC modes differ from one another in QoSsupported by each of the TM. UM and AM, their operational methods aredifferent from one another as well as their detailed functions. So, theRLC needs to be looked into according to its operational mode.

TM RLC is a mode that any overhead is not attached to RLC service dataunit (hereinafter abbreviated SDU) delivered from a higher layer inconfiguring RLC protocol data unit (hereinafter abbreviated PDU). Inparticular, since an RLC transmits SDU transparently, it is called TMRLC. Due to such a characteristic, TM RLC plays the following roles inuser and control planes. In the user plane, since data processing timewithin RLC is short, TM RLC performs a real-time circuit data transferof a voice or streaming in a circuit service domain (hereinafterabbreviated ‘CS domain’). Meanwhile, in the control plane, since thereis no overhead within RLC, the RLC is responsible for a transmission ofan RRC message from an unspecific UE in case of an uplink or atransmission of an RRC message broadcast to all UEs within a cell incase of a downlink.

Unlike the transparent mode, a mode of adding an overhead in RLC iscalled a non-transparent mode that is classified into an unacknowledgedmode (UM) and an acknowledged mode (AM). By attaching a PDU headerincluding a sequence number (hereinafter abbreviated SN) to each PDU totransfer, UM RLC enables a receiving side to know which PDU is lost inthe course of transmission.

In aspect of a transmitting side RLC, a transmitting side operating inUM does not check whether a receiving side receives a corresponding PDUcorrectly. So, the transmitting side does not transmit a PDU that wastransmitted once. In an aspect of a receiving side RLC operating in UM,a receiving side checks which PDU is lost through a sequence number of areceived PDU. The receiving side does not further expect a reception ofthe PDU decided as lost and immediately delivers the successfullyreceived SDU to an upper layer. For instance, if a specific UM RLCreceives an RLC PDU having a sequence number of ‘6’ after havingreceived an RLC PDU having a sequence number of ‘3’, the correspondingUM RLC decides that a reception of an RLC PDU having a sequence numberof ‘4’ or ‘5’ fails and does not expect a further reception of the PDUsany more.

Owing to this function, the UM RLC is mainly responsible for atransmission of real-time packet data such as a broadcast/multicast dataand a voice (e.g., VoIP) or streaming of a packet service domain(hereinafter abbreviated PS domain) in a user plane or a transmission ofan RRC message needing no acknowledgement among RRC messages transmittedto a specific UE or a specific UE group within a cell in a controlplane.

Like the UM RLC, an AM RLC as one of the non-transparent modesconfigures a PDU by attaching a PDU header including an SN thereto. Yet,the AM RLC differs from the UM RLC in that a receiving side makesacknowledgement to a PDU transmitted by a transmitting side. The reasonwhy the AM RLC of the receiving side makes acknowledgement is becausethe receiving side can make a request for a retransmission of a missingPDU by the transmitting side. And, this retransmission function is themost outstanding feature of the AM RLC. So, the object of the AM RLC isto guarantee an error-free data transmission through the retransmission.Owing to this object, the AM RLC mainly takes charge of a transmissionof non-real-time packet data such as TCP/IP of PS domain in a userplane.

The UM RLC is explained in detail as follows.

First of all, the UM RLC establishes and manages the followingenvironmental variables.

First of all, VR(US) indicates a next reception number. This value meansa value right next to an SN value of a last received RLC PDU. Namely, ifan SN value of ‘x’ is received, VR(US) is set to ‘x+1’.

In case of receiving RLC SDUs (service data units) from an upper layer(e.g., an upper layer of UM RLC), a UM RLC of a transmitting sidegenerates an RLC PDU by adjusting the received RLC SDUs into a suitablesize by segmentation and concatenation and then delivers the generatedRLC PDU to a lower layer (e.g., a lower layer of the UM RLC). And, theUM RLC includes a length indicator (hereinafter abbreviated LI), whichindicates a position of a boundary of RLC SDU within the RLC PDU, inorder to enable a receiving side to recover the RLC SDUs from the RLCPDU.

In this case, a sequence number SN is represented as 7 bits. Byrepresenting the SN in a simple from, it is able to raise a transportefficiency of data to be delivered in a manner of reducing a header partfrom each RLC PDU. Hence, sequence numbers substantially transferred bybeing included in the RLC PDU are values belonging to a range between0˜127. So, the transmitting side sequentially assigns sequence numbersto the respective RLC PDUs from zero to use and then assigns sequencenumbers from zero to reuse after assigning 127. Like this, a case that asequence number starts to be reused from such a lower value as zero froma higher value of ‘127’ can be regarded as a case that ‘wrap-around’ hasoccurred. Hence, RLC PDUs after the occurrence of ‘wrap-around’ are theRLC PDUs that must be delivered behind RLC PDUs prior to the occurrenceof ‘wrap-around’.

The receiving side always checks the SN of the received RLC PDU. If theSN of the received RLC PDU is smaller than that of the last received RLCPDU, the receiving side decides that ‘wrap-around’ has occurred. And,the entire RLC PDUs received after the ‘wrap-around’ occurrence areregarded as RLC PDUs generated behind the previously received RLC PDU.

FIG. 3 is a flowchart of a process for receiving RLC PDU from a lowerlayer in a UM RLC operation of a receiving side according to a relatedart.

Referring to FIG. 3, a receiving side receives an RLC PDU having an SNvalue (S300).

Subsequently, VR(US) is reset to correspond to the SN value of thereceived RLC PDU (S301).

If an updated width of the VR(US) value is not ‘1’ in the step S301, itis decided that there exists a lost RLC PDU (S302). RLC SDUs associatedwith the RLC PDUs decided as lost are then deleted (S303).

If an updated width of the VR(US) value is ‘1’, the following steps areexecuted.

First of all, after a recovery process has been carried out using thesuccessfully received RLC PDUs, successfully recovered RLC SDUs aredelivered to an upper layer of RLC (S304).

After the delivery (S304), the whole process is ended (S305).

An RRC state and connection method of a UE are explained in detail asfollows.

First of all, an RRC state means whether an RRC of UE is in a logicalconnection to an RRC of UTRAN. If the RRC of the UE is in the logicalconnection to the RRC of the UTRAN, it is called an RRC connected state.Otherwise, it is called an RRC idle state.

Since there exists an RRC connection for a UE in an RRC connected state,a UTRAN is able to recognize an existence of the corresponding UE by acell level. Hence, the UTRAN is able to effectively control the UE. Yet,a UTRAN is unable to recognize an existence of a UE in an RRC idlestate. A core network (hereinafter abbreviated CN) manages thecorresponding UE by a location area level or a routing area level thatis an area unit greater than a cell. In particular, an existence ornon-existence of an UE in an RRC idle state can be just recognized by alarge area unit. And, the UE in the RRC idle state has to enter an RRCconnected state to receive a general mobile communication service suchas a voice and data.

When a user turns on a power of UE for the first time, the UEpreferentially makes a search for a suitable cell and then stays in anRRC idle state at the corresponding cell. The UE in the RRC idle stateestablishes an RRC connection with an RRC of UTRAN through an RRCconnection procedure if necessary for the RRC connection. The UE thenmakes a transition to an RRC connected state.

There are several cases for a UE in an RRC idle state to establish anRRC connection. For instance, the RRC connection is established if anuplink data transport is needed due to a user's attempt to make a callor the like. For another instance, the RRC connection is established ifa paging message is received from UTRAN.

In order for a UE in an RRC idle state to establish an RRC connectionwith UTRAN, the above-explained RRC connection procedure needs to beexecuted.

The RRC connection procedure mainly consists of the three steps of anRRC connection request message transmission to a UTRAN from a UE, an RRCconnection setup message transmission to the UE from the UTRAN and anRRC connection setup complete message transmission to the UTRAN from theUE. This RRC connection procedure is shown in FIG. 4.

FIG. 4 shows a flowchart of an RRC connection procedure according to arelated art.

Referring to FIG. 4, an RRC connection request step (S401) is explainedas follows.

First of all, if a UE in an RRC idle state attempts to establish an RRCconnection due to a calling trial, a response to a paging of a UTRAN orthe like, the UE preferentially sends an RRC connection request messageto the UTRAN.

In this case, the RRC connection request message contains an initial UEidentity, an RRC connection establishment cause and the like.

The initial UE identity is a unique identity of the UE and enables thecorresponding UE to be globally identified regardless of the UE'slocation. And, there are various kinds of the RRC connectionestablishment causes such as a calling trial, a response to a paging andthe like.

The UE drives a timer as soon as transmits the RRC connection requestmessage. The UE retransmits the RRC connection request message unlessreceiving an RRC connection setup message or an RRC connection rejectmessage from the UTRAN until the timer expires. IN this case, a maximumtransmission count of the RRC connection message is limited to aspecific value.

An RRC connection setup step (S402) is explained as follows.

The UE having received the RRC connection request message accepts an RRCconnection request made by the UE if radio resources are sufficient. TheUE then transmits an RRC connection setup message as a response messageto the UE. In this case, the RRC connection setup message is transmittedby including a radio network temporary identity (hereinafter abbreviatedRNTI), radio bearer setup information and the like together with theinitial UE identity. And, the radio network temporary identity is a UEidentity that enables the UTRAN to identify the UE in the RRC connectedstate. The identity is used only if there exists an RRC connection. And,the identity is used within the UTRAN only.

After the RRC connection has been set up, the UE communicates with theUTRAN using the radio network temporary identity instead of using theinitial UE identity. If the initial UE identity, which is the uniqueidentity of the UE, is frequently used, it may be drained away. So, theinitial UE identity is temporarily used in the RRC connection procedure.Thereafter, the radio network temporary identity is used.

And, an RRC connection setup complete step (S403) is explained asfollows.

First of all, the UE having received the RRC connection setup messagechecks whether the received message is a message supposed to be sent tothe UE itself in a manner of comparing the initial UE identity includedin the message to its identity.

If the message is the message supposed to be sent to the UE itself as aresult of the check, the UE stores the radio network temporary identityassigned by the UTRAN and then transmits an RRC connection setupcomplete message to the UTRAN using the stored radio network temporaryidentity. In this case, UE capability information and the like areincluded in the RRC connection setup complete message.

In case of transmitting the RRC connection message successfully, the UEestablishes the RRC connection with the UTRAN for the first time andthen makes a transition to an RRC connected state.

Meanwhile, the RRC connection request message is transmitted on a randomaccess channel (hereinafter abbreviated RACH), whereas the RRCconnection setup message is transmitted on a forward access channel(hereinafter abbreviated FACH).

However, a network is unable to recognize an existence of the UE untilthe RRC connection setup is completed. So, the UE sends the RRCconnection request message as a first message using the RACH shared byall UEs. And, the RACH is delivered to a connection management end ofthe network via a logical channel called a common control channel(hereinafter abbreviated CCCH) shared by the entire UEs. Likewise, afirst message delivered to the UE from the network is delivered on achannel received by the entire UEs in common. Moreover, since aconnection setup method and channel information corresponding to the UEonly are included in the RRC connection setup message as the firstmessage, the network is able to deliver the message to the correspondingUE via a common channel only until the UE receives the RRC connectionsetup message. In this case, the RRC connection setup message isdelivered on CCCH. And, this message is transmitted in a UM RLC mode.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method of processingcontrol information in a mobile communication system that substantiallyobviates one or more problems due to limitations and disadvantages ofthe related art.

An object of the present invention is to provide a method of processingcontrol information in a mobile communication system, by which an RRCconnection setup can be quickly completed.

Another object of the present invention is to provide a method ofprocessing control information in a mobile communication system, bywhich control information can be processed without an unnecessarystandby of a mobile terminal.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod of processing control information in a mobile communicationsystem according to the present invention includes the steps ofreceiving a plurality of protocol data units transmitted plural timefrom a transmitting side via one common logical channel by an RLC (radiolink control) entity operating in a UM (unacknowledged mode) and havinga receiving window and a timer, re-ordering a plurality of the receivedprotocol data units using sequence numbers of a plurality of thereceived protocol data units, the receiving window and the timer,reassembling at least one service data unit by processing a plurality ofthe re-ordered protocol data units, and delivering the at least oneservice data unit.

In another aspect of the present invention, a method of processingcontrol information in a mobile communication system includes the stepsof transmitting a first control message for a control of a radioresource to a network, observing a specific channel receiving from thenetwork a second control message indicating whether it received thefirst control message, and retransmitting the first control message tothe network according to a result of the observing step.

In another aspect of the present invention, a method of processingcontrol information in a mobile communication system includes the stepsof deciding whether a first control message for a control of a radioresource is received from a mobile terminal, transmitting a secondcontrol message indicating whether it received the first control messageto the mobile terminal via a specific channel according to a result ofthe deciding step, and re-receiving the first control message from themobile terminal according to whether the mobile terminal receives thesecond control message.

In another aspect of the present invention, a method of processingcontrol information in a mobile communication system includes the stepsof receiving at least one protocol data unit from a lower layer, if atleast one service data unit fails to be recovered from the at least onereceived protocol data unit, deciding whether a specific area of the atleast one service data unit is successfully received, and deliveringdata including the specific area to an upper layer according to a resultof the deciding step.

In another aspect of the present invention, a method of processingcontrol information in a mobile communication system includes the stepsof transmitting a control message for a control of a radio resource to anetwork, receiving at least one data protocol unit corresponding to aresponse message for the control message and including an identity foridentifying a specific user equipment from the network, deciding whetherat least one service data unit can be recovered from the at least onereceived protocol data unit, and retransmitting the control messageaccording to a result of the deciding step.

In a further aspect of the present invention, a method of processingcontrol information in a mobile communication system includes the stepsof receiving a control message for a control of a radio resource from amobile terminal, including an identity for identifying a specificterminal in at least one protocol data unit corresponding to a responsemessage for the control message, transmitting the at least one protocoldata unit to the mobile terminal, and re-receiving the control messagefrom the mobile terminal according to whether the mobile terminalsuccessfully receives the at least one protocol data unit.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a block diagram of a network structure of UMTS (universalmobile telecommunications system);

FIG. 2 is a diagram of architecture of a radio protocol used for UMTS;

FIG. 3 is a flowchart of a process for receiving RLC PDU from a lowerlayer in a UM RLC operation of a receiving side according to a relatedart;

FIG. 4 shows a flowchart of an RRC connection procedure according to arelated art; and

FIG. 5 is a flowchart of a re-ordering procedure according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

First Embodiment

A signal transmitting/receiving method according to a first embodimentof the present invention is able to enhance the related art RRCconnection setup procedure.

As mentioned in the foregoing description, an RRC connection setupmessage is transmitted via CCCH. In this case, the CCCH is used by a UMRLC. In doing so, messages are delivered via a common physical channelsince a physical channel for a specific UE is not established. Namely,the RRC connection setup message is not delivered to a intended UE, viaa dedicated physical channel. Hence, it is less probable that thecorresponding UE will receive the message correctly.

Despite that a UE transmits an RRC connection request message, that anetwork successfully receives the RRC connection request message andthat the network correctly transmits an RRC connection setup message tothe UE, It may frequently happen that the UE fails to receive the RRCconnection setup message due to a CCCH's characteristic as a commonchannel and a UM RLC's characteristic of not receiving ACK. In thiscase, after waiting for an expiration of a T300 timer, if failing toreceive the RRC connection setup message until the expiration, the UEagain transmits the RRC connection request message to the network. Sincethe T300 timer is actually set to 4 seconds in a UMTS system, a 4-secondconnection delay takes place each time the UE fails in receiving the RRCconnection setup message. This connection delay provides a bad qualityto a user.

A signal transmitting/receiving method according to an embodiment of thepresent invention proposes a method of transmitting a message to a UEfrom a network more reliably and quickly. In the embodiment of thepresent invention, in case that a network delivers an RRC message to aUE via a common physical channel or a common transfer channel, an RLCentity transmits RLC PDUs, which are generated for one RLC SDU, at leastonce.

In particular, the present invention proposes a method that, in case ofreceiving an RRC message via a common physical channel or a commontransfer channel, a UE is able to correctly recover RLC SDUs to deliverto an upper layer in spite of receiving the same RLC PDUs plural times.

In particular, the present invention proposes an RLC entity that isoperated using a re-ordering timer and a receiving window. Namely, inthe present embodiment, the receiving window is used so that RLC PDUscan be sequentially stored according to SN in spite of being transmittedplural times. And, in the present embodiment, in case of using thereceiving window, the re-ordering timer is used to prevent an operationfrom being delayed in the course of standing by for a reception of aspecific RLC PDU.

In particular, in the above process, the present invention proposes thata network transmits the message via an RLC in an unacknowledged mode.

Preferably, in the above process, it is proposed that the network is anRNC. Preferably, in the above process, it is proposed that the RRCmessage is mapped to a common logical channel. Preferably, in the aboveprocess, it is proposed that the common logical channel is CCCH.

Preferably, in the above process, it is proposed that the RRC message isdelivered via a common transfer channel. Preferably, in the aboveprocess, it is proposed that a common logical channel is mapped to thecommon transfer channel. Preferably, in the above process, it isproposed that the common transfer channel is FACH.

Preferably, in the above process, it is proposed that the commontransfer channel is mapped to the common physical channel. Preferably,in the above process, it is proposed that the RRC message is deliveredvia the common physical channel. Preferably, in the above process, it isproposed that the common physical channel is S-CCPCH (secondary commoncontrol physical channel).

More specifically, the present invention proposes that a network shouldtransmit an RRC message plural times to raise an RRC message receptionsuccess probability of a UE.

For this, the present invention proposes an RLC entity operating methodfor a case that a UE receives the same RLC PDU at least once via onecommon channel. Namely, in case that a UM RLC receives the same RLC PDUfor the same RLC SDU plural times, the present embodiment proposes amethod of processing the received RLC PDU using a receiving window and are-ordering timer.

Preferably, the RLC PDU processing method using the receiving windowmeans a processing method that the UM RLC manages a range of SN valuesof the RLC PDU that is expected to be received by the UM RLC itselfbased on the received RLC PDU.

Preferably, in case that the RLC PDU received by the UM RLC remains inthe receiving window by not being reserved for reassembly, the RLC PDUprocessing method using the re-ordering timer means a method ofprocessing the RLC PDU regardless of a reception of another PDU afterduration according to the operated re-ordering timer.

Preferably, in case of receiving a re-ordering indication from an upperlayer, the UM RLC operates by deciding that the same RLC PDU can bereceived via the channel at least once. In case of not receivingre-ordering indication from an upper layer, the UM RLC operates bydeciding that the same RLC PDU can be received just once for one logicalchannel like the related art method.

Preferably, the UE will receive information for the re-orderingindication from a network. When UEs receive the RRC messages via systeminformation, the network notifies information indicating whether the UEsexecute the re-ordering. An RRC of the UE informs an RLC how the UEoperates via the re-ordering indication based on the information.

In other words, in case of attempting to perform a more reliable RRCmessage transmission, the network notifies that a re-ordering functionis used in sending the RRC message, via a channel and message fordelivering the system information. If the network does not send the RRCmessage using the re-ordering function, the network notifies that there-ordering function is not used via the system information or does notnotify whether to use the re-ordering function.

If the system information instructs that the re-ordering function isused for the transmission of the RRC message, the UE uses there-ordering function after having received the system information. Inparticular, the UE processes the RLC entity mapped to the channelcarrying the RRC message using the re-ordering function. Yet, in case ofreceiving the system information instructing that the re-orderingfunction is not used (e.g., a case that a deactivation of there-ordering function in the RRC message transmission is instructed orthat the information indicating whether to activate the re-orderingfunction is not provided), the UE does not use the re-ordering function.In particular, the RLC entity mapped to the channel carrying the RRCmessage is processed not using the re-ordering function.

A presence or non-presence of the activation of the re-ordering functioncan be identified according to a release number instructed by the systeminformation. In particular, if the system information instructs that acommunication specification is the 3GPP release-7 or the 3GPP release-8,it is able to activate the re-ordering function.

In case of using the re-ordering function, it is preferable that thenetwork provides various setup values for the re-ordering function. Inthis case, the setup values include a size of a receiving window, atimer value of a re-ordering timer and the like. In case of receivingthe setup values via the system information, the UE performs a setup forthe RLC entity using the received values.

The above-explained embodiment of the present invention is explainedwith reference to FIG. 5 as follows.

FIG. 5 shows an example of a method of setting a receiving window and are-ordering timer.

Variables for the receiving window and re-ordering timer proposed by thepresent invention are explained in the following description.

First of all, a receiving window corresponds to a range of an SN valueof an RLC PDU received and processed by an RLC entity. The range of thereceiving window is equal to or greater than a value resulting fromsubtracting a receiving window size from VR(UDH) that will be explainedlater.

The receiving window size is a value that indicates a size of thereceiving window.

VR(UDR) indicates a reception standby number of the receiving window.This value is used in case that a re-ordering is set. And, this valuemeans a value next to an SN value of a last RLC PDU that is sequentiallyreceived. An initial value of the VR(UDR) is determined in a followingmanner. First of all, if VR(UDH) is set according to an RLC PDU that isfirst received after initialization of the RLC entity, the initial valueof the VR(UDR) is set to a value resulting from adding ‘1’ to a value ofsubtracting a value of the receiving window size from a value of theVR(UDH).

VR(UDH) indicates a maximum reception number of a receiving window. Thisvalue is used in case that a re-ordering is set. This value means anupper limit value of a receiving window in a UM RLC. And, this valuemeans a value next to a greatest value of an SN value of a received RLCPDU. If an RLC PDU having an SN (=x) deviating from a range of apreviously set window is received, VR(UDH) is determined in a followingmanner. If an RLC PDU, which is ‘x’, is received, VR(UDH) is set to avalue resulting from adding ‘1’ to ‘x’. An initial value of VR(UDH) isdetermined as an SN of an RLC PDU that is first received afterinitialization of an RLC entity.

VR(UDT) indicates a timer instruction number. This value is used only ifa re-ordering is set. This value is set to an SN value corresponding toan RLC PDU of which re-ordering timer is set. And, an initial value iszero.

In a present embodiment, a UM RLC receives a new RLC PDU from a lowerlayer. According to whether a re-ordering is activated, if there-ordering is not set up, the UM RLC operates as the related art UM RLCdoes. If the re-ordering is set up, the UM RLC operates according to anSN value of a received RLC PDU, a receiving window and a re-orderingtimer (S1).

In the above procedure, the meaning that the UM RLC operates like therelated art UM RLC indicates that VR(US) is updated according to an SNvalue of a received RLC PDU, that it is decided that there is a lost PDUif an update width of the VR(US) is not ‘1’, that RLC PDUs associatedwith the RLC PDUs decided as lost are deleted, and that RLC PDUs decidedas successfully received are recovered to be delivered to an upperlayer. In the above procedure, if the update width of the VR(US) is ‘1’,it is decided that there is no lost PDU. RLC PDUs are recovered based onthe received RLC PDUs. The recovered RLC PDUs are then delivered to anupper layer.

An RLC SDU associated with a specific PDU indicates the RLC SDU ifpartial data of the RLC SDU or a length indication (LI) indicating anend of the RLC SDU is included in the specific RLC PDU.

The meaning of the above described ‘UM RLC operates according to SN ofRLC PDU, receiving window and re-ordering timer (S1)’ is explained asfollows.

First of all, a UM RLC checks a newly received RLC PDU using an SN valueof the RLC PDU, a receiving window and a reception standby number(VR(UDR)) and the corresponding RLC PDU is then processed according to aresult of the check (S2). The RLC PDU is additionally processedaccording to a presence or non-presence of RLC PDU of which SN value isVR(UDR) (S3). Thereafter, a re-ordering timer is additionally processed(S4). Finally, an RLC PDU, of which reassembly is reserved, isadditionally processed (S5).

In the above procedure, the meaning of ‘a UM RLC checks a newly receivedRLC PDU using an SN value of the RLC PDU, a receiving window and areception standby number (VR(UDR)) and the corresponding RLC PDU is thenprocessed according to a result of the check (S2)’ is explained asfollows.

First of all, a UM RLC checks whether an SN value of a received RLC PDUis located within a receiving window.

If the SN value of the received RLC PDU is located within the receivingwindow and if the SN value is smaller than VR(UDR) or if an RLC PDUcorresponding to the SN value is received in advance, the correspondingRLC PDU is deleted.

Otherwise, the corresponding RLC PDU is placed at a position indicatedby the SN value of the RLC PDU within the receiving window.

If the SN value of the received RLC PDU is not located within thereceiving window, the received RLC PDU is placed at a position indicatedby the SN value of the RLC PDU. And, by setting a value of VR(UDH) tothe SN value of the RLC PDU, a position of the receiving window isupdated.

Subsequently, RLC PDUs of which SNs deviate from a range of the updatedreceiving window (i.e., RLC PDUs of which SNs do not exist between alower limit value resulting from subtracting a value of a receivingwindow size from VR(UDH) and an upper limit value of VR(UDH)) among PDUsstored in a receiving buffer provided to a UE are reserved forreassembly. If VR(UDR) is smaller than the updated receiving window,VR(UDR) is updated into a value resulting from subtracting the receivingwindow size from VR(UDH).

In the above procedure, the meaning of ‘The RLC PDU is additionallyprocessed according to a presence or non-presence of RLC PDU of which SNvalue is VR(UDR) (S3)’ is explained as follows.

First of all, if an RLC PDU having a specific SN value exists within areceiving window, RLC PDUs ranging from the RLC PDU to a first RLC PDUthat is not sequentially received are reserved for reassembly. And, avalue of VR(UDR) is updated into an SN value of the first RLC PDU thatis not sequentially received.

In the above procedure, the meaning of ‘a re-ordering timer isadditionally processed (S4)’ is explained as follows.

First of all, if a re-ordering timer, which is operating, exists, a UMRLC checks whether an RLC PDU having an SN value of VR(UDT) is reservedfor reassembly. If the corresponding RLC PDU is reserved for reassemblyaccording to a result of the check, the re-ordering timer is stopped.

Subsequently, the UM RLC again checks whether a re-ordering timer, whichis operating, exists. If there is no re-ordering timer that is operatingas a result of the check, the UM RLC checks whether there are RLC PDUswhich exist within a receiving buffer and of which reassembly is notreserved. If there are RLC PDUs which exist within a receiving bufferand of which reassembly is not reserved, a re-ordering timer isre-driven for a RLC PDU corresponding to a highest SN value among thePDUs and VR(UDT) is updated into the SN value of the RLC PDU.

In the above procedure, the meaning of ‘an RLC PDU, of which reassemblyis reserved, is additionally processed (S5)’ is explained as follows.

First of all, for an RLC PDU of which reassembly is reserved, if thereare RLC PDUs failing to be received, RLC SDUs associated with the RLCPDUs failing to be received are deleted. RLC SDUs are recovered (i.e.,reassembled) based on RLC PDUs having been received. The recovered RLCPDUs are then delivered to an upper layer. In this case, an RLC SDUassociated with a specific RLC PDU means an RLC PDU corresponding to acase that partial data of the RLC SDU or an LI (length indication)indicating an end of the RLC PDU is included in the specific RLC PDU.

In the above procedures, if the re-ordering timer expires at any time, areservation is made to reassemble RLC PDUs equal to or smaller than theVR(UDT) value. A reservation is made to reassemble RLC PDUs ranging fromthe RLC PDU of VR(UDT) to the first RLC PDU not sequentially received.And, the VR(UDR) is updated to the SN value of the first RLC PDU that isnot sequentially received.

As a result of completion of the above procedures, if there are RLC PDUswhich exist within the receiving buffer and of which reassembly is notreserved, the re-ordering timer is re-driven for the RLC PDUcorresponding to the highest SN value among the PDUs. And, the VR(UDT)is updated into the SN value of the RLC PDU. If the PDU of the SNcorresponding to the VR(UDT) is removed from the receiving buffer, there-ordering timer is stopped. When RLC PDUs are stacked in the receivingbuffer, if the re-ordering timer is not activated, the re-ordering timerstarts to operate and the VR(UDT) is designated as the SN value of thePDU.

FIG. 5 shows a detailed example of implementing the above-explainedoperations through the variables. Individual steps shown in FIG. 5 areexplained in detail as follows.

First of all, an RLC PDU of which SN value is ‘RSN’ is received from alower layer of a UM RLC (S5010).

If a re-ordering is set up (S5020), the operation is executed from astep S5050. If the re-ordering is not set up (S5020), the operation isexecuted from a step S5030.

Subsequently, VR(US) is updated (S5030). If an update width of VR(US) isnot ‘1’ (S5031), SDUs associated with PDUs decided as lost are deleted(S5032). In this case, RLC PDUs decided as lost means the RLC PDUs eachof which has a sequence number equal to or greater than the VR(US) priorto the update or smaller than ‘RSN’.

RLC SDU is recovered using a received RLC PDU. The recovered RLC PDU isdelivered to an upper layer (S5040). A procedure is then ended (S5041).

If ‘RSN’ is not included in an area of a receiving window (S5050), theoperation is executed from a step S5070. If ‘RSN’ is included in thearea of the receiving window (S5050), the operation is executed from astep S5060.

If ‘RSN’ is smaller than VR(UDR) or if a received RLC PDU is the PDUthat was previously received (S5060), the corresponding RLC PDU isdeleted (S5062). Otherwise, the corresponding RLC PDU is placed at aposition instructed by ‘RSN’ within a receiving buffer (S5061). Theoperation is then executed from a step S5100.

A received RLC PDU is placed at a position instructed by ‘RSN’ andVR(UDH) is then updated into a value resulting from adding ‘1’ to ‘RSN’(S5070).

RLC PDUs, each of which has an SN value smaller than an updatedreceiving window (i.e., each of which is located outside the receivingwindow), are reserved for reassembly (S5080).

If VR(UDR) is located below the updated receiving window (S5090),VR(UDR) is updated into a value resulting from subtracting a receivingwindow size from VR(UDH) (S5091).

If an RLC PDU corresponding to VR(UDR) is not stored in the receivingbuffer (S5100), the operation is executed from a step S5120. Otherwise,the operation is executed from a following step S5110.

RLC PDUs ranging from an RLC PDU corresponding to VR(UDR) to a first RLCPDU that is not sequentially received within the receiving buffer arereserved for reassembly (S5110). Subsequently, VR(UDR) is updated intoan SN value of the first RLC PDU that is not sequentially received(S5111).

If a re-ordering timer is not activated (S5120), the operation isexecuted from a step S5140. Otherwise, the operation is executed from astep S5130.

If an RLC PDU corresponding to VR(UDT) is reserved for reassembly(S5130), the re-ordering timer is stopped (S5131).

If the re-ordering timer is operating (S5140), the operation is executedfrom a step S5170. Otherwise, the operation is executed from a stepS5150.

If there is an RLC PDU stored in receiving buffer and not reserved forreassembly (S5150), the operation is executed from a step S5160.Otherwise, the operation is executed from a step S5170.

The re-ordering timer is driven for an RLC PDU having a greatest SNvalue among RLC PDUs not reserved for the reassembly within thereceiving buffer and VR(UDT) is set to the SN value of the PDU (S5160,S5161).

For RLC PDUs of which re-ordering is reserved, RLC SDUs associated withRLC PDUs decided as lost are deleted. For RLC PDUs having been received,RLC SDUs are recovered. The recovered RLC PDUs are delivered to an upperlayer. The operation is then ended (S5170).

The above-explained whole operation is summed up as follows.

First of all, as mentioned in the foregoing description, a receivingwindow is used as a means for processing a repeatedly received UM RLCPDU. In particular, a repeatedly received UM RLC PDU is processed usingVR(UDR) indicating a position of a sequentially received RLC PDU,VR(UDH) indicating an upper limit of the receiving window and a size ofthe receiving window.

In case of using the receiving window, if there is a first received RLCPDU, the first received RLC PDU is stored and an area of the receivingwindow is updated. If there is an RLC PDU that is received repeatedly orsequentially in advance, the corresponding RLC PDU is deleted. In thiscase, upper and lower limits of the receiving window are updated tomanage RLC PDUs that are not sequentially received.

In case of using the receiving window, if specific RLC PDUs are receivedplural times or sequences of the specific RLC PDUs are not sequential,it is advantageous that the PDUs can be sequentially stored. Yet, inthis case, it may happen that an RLC PDU of which reception isimpossible is waited for endlessly. So, RLC PDUs failing to be receivedwithin a time limit according to a re-ordering timer and theirassociated RLC SDUs are deleted. In particular, according to anoperation of the re-ordering timer, RLC PDUs having SNs equal to orsmaller than VT(UDT) are regarded as reception-impossible RLC PDUs andare then deleted.

In the above process, an operation of a network should consider a UEfailing to support a re-ordering function as well as a UE supporting there-ordering function. In this case, the UE failing to support there-ordering function means a UE performing an operation of the relatedart UM RLC. This UE always wishes that an SN of a received RLC PDUshould be incremented by ‘1’ each time. And, this UE assumes that a lossof an RLC PDU takes place if an increment of the SN exceed ‘1’. Hence,in case that the network supports the re-ordering function, if atransmission sequence of RLC PDUs for one RLC SDU is randomly changed,the UE failing to support the re-ordering function is unable to per forma reception correctly.

Therefore, the present invention intends to propose a method oftransmitting RRC messages correctly to a UE for which an RLC entity of anetwork supporting a re-ordering function does not support there-ordering function.

In particular, the present invention proposes that RLC PDUs for one RLCSDU should be sequentially transmitted. For instance, if PDUsconfiguring RLC SDU 1 include RLC PDU 1, RLC PDU 2 and RLC PDU 3, theRLC PDUs are always transmitted to a UE in sequence of RLC PDU 1→RLC PDU2→RLC PDU 3. Even if one RLC PDU is transmitted at least twice, thepresent invention proposes that the RLC PDUs should be transmitted insequence of RLC PDU 1→RLC PDU 2→RLC PDU 3→RLC PDU 1→RLC PDU 2→RLC PDU 3.

In transmitting a message from a network to a UE, if RLC PDU istransmitted plural times, the present invention proposes that one RLCPDU should be consecutively transmitted as many as a count ofretransmissions. For instance, if RLC PDUs include RLC PDU 1, RLC PDU 2and RLC PDU 3 and if one RLC PDU is transmitted twice each, the presentinvention proposes that the RLC PDUs should be transmitted in a mannerof RLC PDU 1→RLC PDU 1→RLC PDU 2→RLC PDU 2→RLC PDU 3→RLC PDU 3.

In transmitting consecutive RRC messages, if one targets a UE supportinga re-ordering and if the other targets a UE not supporting are-ordering, the present invention proposes that parts of two messagesshould not be included in one RLC PDU. In particular, the presentinvention proposes that parts of at least two RLC SDUs should not beincluded in one RLC PDU.

And, the present invention proposes that a re-ordering function shouldbe selectively used. In particular, the present invention proposes thata network should use a function of transmitting one RLC PDU severaltimes to a UE supporting a re-ordering function only based on releaseinformation of UE or information indicating a presence or non-presenceof a re-ordering function supported by the UE. For this, the presentinvention proposes that a UE should inform a network of a presence ornon-presence of its re-ordering function support in RRC connection.

Second Embodiment

A second embodiment according to the present invention proposes a methodof preventing a UE from awaiting a response made by a networkunnecessarily long.

In particular, if an RRC message sent by a UE is not received by anetwork, it is meaningless for the UE to await a response from thenetwork.

For instance, a UE awaits a response from a network after having sent anRRC connection request message. If there is no response until aretransmission timer expires, the UE sends the RRC connection requestmessage again. In this case, if the RRC connection request message sentby the UE is not correctly forwarded to the network, it is meaninglessfor the UE to await the response made by the network. Hence, the UEpreferably retransmits an RRC message such as an RRC connection requestmessage and the like right after having recognized that a messagetransmitted by the UE itself had not been correctly forwarded to thenetwork.

For this, in case of sending an RRC message on an uplink shared channel,if there is no response from a network within a predetermined time toindicate that the message has been correctly received, a UE retransmitsthe RRC message.

Preferably, in the above process, the present invention proposes thatthe network should include an RNC. Preferably, in the above process, thepresent invention proposes that the RRC message should be mapped to acommon logical channel. More preferably, in the above process, thepresent invention proposes that the common logical channel shouldinclude CCCH (common control channel).

Preferably, in the above process, the present invention proposes thatthe RRC message should be transferred via a common transfer channel.More preferably, in the above process, the present invention proposesthat the common logical channel should be mapped to the common transferchannel. More preferably, in the above process, the present inventionproposes that the common transfer channel should include RACH (randomaccess channel).

Preferably, in the above process, the present invention proposes thatthe common transfer channel should be mapped to a common physicalchannel. More preferably, in the above process, the present inventionproposes that the RRC message should be transferred via the commonphysical channel. More preferably, in the above process, the presentinvention proposes that the common physical channel should include PRACH(physical random access channel).

In the above process, in case of receiving the RRC message from the UE,the network immediately makes a response to the received message. And,the response can be made in various ways.

In a first example of making a response immediately, in case ofreceiving a message from a UE via the channels, a network immediatelytransmits acknowledgement to the UE. For instance, in case of receivingan RRC connection request message, a network informs the UE that it hasreceived the RRC connection request message. The UE, which has receivedthis information, then stands by until receiving a response message forthe RRC message from the network. For instance, the UE havingtransmitted an RRC connection request message receives anacknowledgement for the transmitted message and then awaits an RRCconnection setup message.

In the above process, in case of not receiving the acknowledgement fromthe network within a predetermined time after having transmitted the RRCmessage via the channel, the UE immediately retransmits the RRC message.

It should be noted that the acknowledgement information means theinformation indicating whether the network has received the RRC messagesent by the UE successfully. For instance, the related art RRCconnection setup message, which is the message for the RRC connectioninstead of indicating a presence or non-presence of a successfulreception of a response message for an RRC connection request message,id discriminated from the acknowledgement information.

Preferably, in the above process, the acknowledgement message sent bythe network to the UE is an RRC message.

Preferably, in the above process, the present invention proposes thatthe network should use a special physical channel to send theacknowledgement for the RRC message transmitted by the UE.

In a current transmission on RACH, a preamble part is acknowledged via achannel called AICH (acquisition indication channel). So, a response fora message part transmitted by a UE can be transmitted to the UE only viaa channel physically specified to a specific UE. In particular, anacknowledgement can be made via a physical channel for a specific UEonly.

For instance, in case of receiving an RRC connection request message, anetwork informs a UE that it has received the RRC connection requestmessage using a physical channel. The UE having received thisinformation stands by until receiving a response message for the RRCmessage, which was sent by the UE itself, from the network. Forinstance, in case of transmitting an RRC connection request message, aUE awaits an RRC connection setup message after having received acorresponding acknowledgement.

In the above process, in case of not receiving the acknowledgement viathe physical channel from the network within a predetermined time afterhaving transmitted the RRC message via the channel, the UE immediatelyretransmits the RRC message.

In the above process, the physical channel, via which the UE performsthe acknowledgement, is transmitted to the UE via a downlink physicalchannel with a duration after the UE has transmitted the RRC message orafter the UE has performed a data transmission via an uplink physicalchannel. And, the physical channel is able to transmit 1-bit informationto the UE.

In a second example of making a response immediately, a network havingreceived an RRC message from a UE informs the UE of an estimated time atwhich the network will send a response. Substantially, in case of beingoverloaded, the network will preferentially handle a job having a highpriority. Although an RRC connection request message having sent by aspecific UE is correctly received by a network, if jobs having highpriorities are left undone, a maximum time T300 for the UE to await aresponse message may be exceeded. So, if the UE retransmits the RRCconnection request message, it would result in a job overload of thenetwork. Hence, it would be helpful if the network informs the UE of anestimated time for sending a response to the UE. The UE receives themessage and then stands by for the corresponding time. Even if a timert300 expires in the course of the standby, the UE awaits an RRC responsemessage for the time informed by the network. In case of failing toreceive the RRC response message from the network, the UE newlytransmits a message or performs another process.

Third Embodiment

A third embodiment according to the present invention proposes a methodof operating a new RLC entity and a format of a new RLC message.

A method of operating a new RLC entity according to a third embodimentof the present invention is explained as follows.

First of all, an RLC entity substantially performs an operation ofdelivering an RLC SDU received from an upper layer or an operation ofrecovering RLC SDU by combining RLC PDUs delivered from a lower layerand delivering the RLC SDU to an upper layer. So, the RLC entityoperates regardless of contents of data transmitted by the RLC entityitself. A defined format of RLC PDU does not indicate what is a targetof the RLC SDU.

Specifically, in case that an RLC entity is mapped to a channel sharedby a plurality of UEs, The RLC entity delivers all kinds of messagesreceived and decoded successfully by the RLC entity itself to an upperlayer. And, the RLC entity discards RLC PDU received in part by the RLCentity itself. Yet, most of RRC messages including an RRC messagetransmitted via a common channel for example indicate which UE istargeted through a specific part (e.g., first part) of the correspondingmessage. Namely, if a specific RLC SDU is segmented into several parts,a receiving side is able to know who is targeted by a corresponding RRCmessage in case of receiving a first part correctly.

In particular, an RLC entity is able to know whether a segment of RLCSDU included in a received RLC PDU is a first part or not using severalLIs. And, a physical layer is able to verify whether each RLC PDU iserroneous. So, for RLC PDU received via a common channel, although anRLC entity is unable to receive all RLC PDUs associated with the RLCPDU, if the RLC PDU includes a first part of a specific RLC SDU and ifthe RLC PDUs are free from CRC error, the RLC entity extracts parts ofthe RLC SDU consecutively extractable from the RLC PDU and consecutiveRLC PDUs from the RLC PDU, delivers the extracted parts to an RRC endand informs the RRC end that it is an incomplete RLC SDU.

An RRC entity having received this checks whether its identity isincluded by interpreting a first part using a portion of the RRCmessage. If its identity is included, the RRC entity recognizes that theRRC message transmitted to the RRC entity fails in transmission and thendecides that it is unable to correctly receive a response awaited by theRRC entity itself. The RRC entity then immediately re-performs an RRCprocess attempted by the RRC entity itself. For instance, if a UE isawaiting an RRC connection setup message and if an RLC entity deliversan RRC message including a first part together with an indication of anincomplete reception, an RRC entity checks whether its identity isincluded in the RRC message delivered in part from the RLC. If itsidentity is included as a result of the check, the RRC entity decidesthat it fails in an RRC connection setup message reception and thenimmediately initiates an RRC connection request message transmissionagain.

Of course, if the RRC connection request message is transmitted byexceeding a maximum allowable count of RRC connection request messagetransmissions, the RRC stops all operations and preferably informs anupper layer of it.

In the above process, the identity of the RRC entity means such anidentity as an RNTI, an IMSI (international mobile station identity)used by an upper layer, a P-TMSI (packet temporary mobile subscriberidentity), a TMSI (temporary mobile subscriber identity) and the like.

In summary, through the above-explained operations, unlike the relatedart, an RLC entity according to the third embodiment of the presentinvention does not delete a corresponding SDU and PDUs corresponding tothe corresponding SDU even if a successful recovery of SDU isimpossible. In particular, in case that a first part of SDU is correctlyreceived, it is able to recognize a recipient of a message. So, aportion of RLC PDU, which is recoverable in case that there is no errorfor RLC PDUs including a first part of a specific RLC PDU, istransmitted to an upper layer.

A format of a new RLC message proposed by a third embodiment of thepresent invention is explained as follows.

First of all, a MAC layer is able to send a response to a UE using ahigher identity of UE. Alternatively, an identity of UE can be added byextending a header part of RLC PDU. In particular, when a network sendsan RRC message via the above channel, an RLC entity to which the RRCmessage is mapped transmits the RRC message by including an identity inan RLC PDU. In case of receiving any one RLC PDU corresponding to theRRC message, a UE is able to know that a network has made a response tothe RRC message having been sent by the UE side. In this case, in caseof failing to completely recover RLC SDU connected to the RLC PDU, theUE is able to send the RRC message to the network by performing an RRCprocess again. Through this, fast transmission and reception of RRCmessage are enabled.

Preferably, the RRC process is a process for transmitting an RRCconnection setup message. Preferably, in the process, the message sentby the network to the UE includes a cell update confirm message. Inparticular, in case that communications between cell-A and cell-B areperformed according to a movement of the UE, a cell update procedure forthe cell-B is executed. In the cell update procedure, a cell updateconfirm message is transmitted by network. In this case, information foridentifying a UE can be included in the cell update confirm message.

Accordingly, the present invention provides the following effects oradvantages.

First of all, a mobile terminal is able to perform an RRC connectionprocess without an unnecessary standby.

Secondly, a cell update procedure can be performed faster by a controlinformation processing method according to the present invention.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of processing a radio link control (RLC) protocol data unit(PDU) at a RLC layer operating in an unacknowledged mode (UM) in amobile communication system, the method comprising: receiving at leastone RLC PDU from a lower layer, the at least one RLC PDU correspondingto an RLC service data unit (RLC SDU); determining whether the at leastone RLC PDU includes a start point of the RLC SDU when the RLC SDU failsto be reassembled from the at least one RLC PDU; reassembling the atleast one RLC PDU to generate a partial RLC SDU if the at least one RLCPDU includes the start point of the RLC SDU; and discarding all of theat least one RLC PDU if none of the at least one RLC PDU includes thestart point of the RLC SDU.
 2. The method of claim 1, wherein thepartial RLC SDU includes regions which are consecutively receivedwithout error from the start point of the RLC SDU.
 3. The method ofclaim 1, wherein the at least one RLC PDU corresponds to a radioresource control (RRC) connection setup message.
 4. The method of claim1, further comprising: transmitting, at the RLC layer, the partial RLCSDU to an upper layer; checking, at the upper layer, whether an identityof the upper layer is included in the partial RLC SDU; transmitting, atthe upper layer, a request message for controlling radio resources to anetwork according to a result of the checking; and re-receiving, at theRLC layer, the at least one RLC PDU corresponding to a response messageto the request message.
 5. The method of claim 4, wherein the identityis included in a header of the at least one RLC PDU.
 6. The method ofclaim 4, wherein the response message is a radio resource control (RRC)connection setup message.
 7. The method of claim 4, wherein the responsemessage is a cell update confirm message.